docs: def check_config(config, data):
      '''Check config file inputs
  
      :param dict config:
           Configuration settings for the function
  
      '''
      essential_keys = ['input_mmin', 'b-value', 'sigma-b']
      for key in essential_keys:
          if not key in config.keys():
              raise ValueError('For KijkoSellevolBayes the key %s needs to '
                               'be set in the configuation' % key)
      if 'tolerance' not in config.keys() or not config['tolerance']:
          config['tolerance'] = 1E-5
  
      if not config.get('maximum_iterations', False):
          config['maximum_iterations'] = 1000
  
      if config['input_mmin'] < np.min(data['magnitude']):
          config['input_mmin'] = np.min(data['magnitude'])
  
      if fabs(config['sigma-b'] < 1E-15):
          raise ValueError('Sigma-b must be greater than zero!')
  
      return config